1. Field of the Invention
The present invention relates to compositions containing a mixture of hydrated calcium hypochlorite, hydrated magnesium sulfate, lime, and one or more basic zinc salts. More particularly, the present invention is directed to stable compositions for use in recreational water that contain a mixture of hydrated calcium hypochlorite, hydrated magnesium sulfate, lime, and one or more basic zinc salts that have long shelf life and high algaecidal and water clarifying properties.
2. Brief Description of Art
Calcium hypochlorite is known for use as a treatment for recreational water, such as pools, spas, hot tubs, and the like. Calcium hypochlorite serves as a source of chlorine, which acts as a disinfectant to keep recreational waters free of water-borne pathogens and other organisms such as algae. The prior art is replete with examples of calcium hypochlorite compositions, for example U.S. Pat. Nos. 3,793,216; 4,201,756; 4,876,003; 4,928,813; 4,145,306; 4,192,763; 4,692,335; 4,865,760; 4,961,872; 5,009,806; 5,164,109; and 5,753,602. In particular, U.S. Pat. Nos. 6,638,446 and 6,984,398 disclose compositions for treatment of recreational water that comprise mixtures of calcium hypochlorite and magnesium sulfate heptahydrate. U.S. Pat. No. 6,969,527 discloses compositions for treatment of recreational water that comprise mixtures of calcium hypochlorite, magnesium sulfate heptahydrate, and lime.
Calcium hypochlorite is available in various forms, including granular solid and tablet solid. Each of these forms have advantages and disadvantages. Granular forms offers lower shipping weight, less storage space, minimal spill hazards and safer handling. Convenient for shock treatment, granular calcium hypochlorite can be broadcast over the surface of the water, added to the pool skimmer with the circulation system running, or pre-diluted in water and added to the pool. Calcium hypochlorite in tablet form offers all the advantages of the granular form but is capable of more effectively delivering a continuous level of chlorination.
Solid forms of calcium hypochlorite generally contain between about 65 to 75 percent by weight available chlorine. However, since calcium hypochlorite breaks down over time, the shelf-life of typical solid calcium hypochlorite is estimated at approximately one year. During that time, when the product is stored in bulk at normal ambient temperatures ranging from approximately 65 to 95° F., the amount of available chlorine can decrease from approximately 70% to below label strength (generally about 65%) in one year or less. This loss can result in a formulation that is less effective at treating recreational water.
There is a need to have available a calcium hypochlorite composition that is stable for a long period of time yet still retains its algaecidal and water clarifying properties. The present invention is believed to be an answer to that need.